Friction anchor for fluid operated downwell pumps

ABSTRACT

A FRICTION ANCHOR FOR FLUID OPERATED DOWNWELL PUMPS WHICH PRECLUDES GROSS MOVEMENT OF THE PUMP IN OPERATION SO AS TO PREVENT CHAFING OF THE SEALS ON THE OUTSIDE DIAMETER OF THE PUMP WHICH ESTABLISH AND MAINTAIN THE HYDRAULIC CIRCUITY. THE FRICTION ANCHOR INCLUDES A LONG, THIN-WALLED, EXPANDABLE SLEEVE ON THE PUMP WHICH FITS CLOSELY WITH THE MATING GRIPPING SURFACE OF A SEAL ON THE WELL CASING O HOUSING SLEEVE. WHEN THE PUMP BECOMES OPERATIONAL, HIGH PRESSURE FROM THE OPERATING FLUID IS APPLIED ON THE INSIDE OF THE EXPANDABLE SLEEVE AND AN ACTUAL INTERFACE FIT BETWEEN THE EXPANDABLE SLEEVE AND THE CASING OR HOUSING SLEEVE SEAL IS SIMULATED.   D R A W I N G

May 30, .1972 P. s. BLOUDOFF FRICTION ANCHOR FOR FLUID OPERATED DOWNWELL PUMPS Filed Oct. 16, 1W0

Fig. 1

OPERATING FLU/D Page S. 5 1. 0000/7 AJTTORNEYS United States Patent O1 fice 3,666,378 FRICTION ANCHOR FOR FLUID OPERATED DOWN WELL PUMPS Peter S. Bloudoff, Whittier, Calif., assignor to Armco Steel Corporation, Middletown, Ohio Filed Oct. 16, 1970, Ser. No. 81,468 Int. Cl. F04b 47/10 US. Cl. 417-358 15 Claims ABSTRACT OF THE DISCLOSURE A friction anchor for fiuid operated downwell pumps which precludes gross movement of the pump in operation so as to prevent chafing of the seals on the outside diameter of the pump which establish and maintain the hydraulic circuitry. The friction anchor includes a long, thin-walled, expandable sleeve on the pump which fits closely with the matinggripping surface of a seal on the well casing or housing sleeve. When the pump becomes operational, high pressure from the operating fluid is applied on the inside of the expandable sleeve and an actual interface fit between the expandable sleeve and the casing or housing sleeve seal is simulated.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to free-type hydraulic pumping systems and is particularly directed to improvements in fluid operated downwell pumps.

(2) Description of the prior art It is becoming increasingly rare when the plans for the producing phase of an oil field do not include a water flood. In practice, water injection is often begun immediately as a means of maintaining bottom hole pressures and thereby extending the flowing life of the field. As a well of this type is pumped, large quantities of water will have to be produced with the oil and the total volumes to be pumped will gradually increase as the percentage of water increases.

Hydraulic downwell pumps disposed at the lower ends of deep wells are especially suited to the aforementioned installations, as their capacity may be controlled by varying their speed, which may be effected by simply adjusting valves to control the volume of power fluid being provided to the particular well. An additional advantage of hydraulic pumps is being able to retrieve a free-type hydraulic pump by circulating it out of the well. Such retrieval becomes even more important due to the short life of equipment which results from the adverse environment which is often encountered in water flood wells.

Since the casing or housing size of a well will generally limit tubing size used therein, such as for example, to 2% inches, there is definitely a limitation on the size of downwell hydraulic pumps which may be utilized within the casing, and thus upon the potential capacity thereof. Accordingly, the capacity of such downwell pumps has been increased by utilizing engines and pumps in tandem.

In a downwell pump the hydraulic circuitry is established and maintained by seals provided on the outside diameter of the pump which contact smooth sleeves within the casing or housing of the bottom hole cavity. In general such seals have proven to be satisfactory. However, high production units now utilize more engines and pumps in tandem in order to increase the capacity thereof, resulting in increased lengths of individual units. Accordingly, this has led to chafing of the aforementioned hydraulic circuitry seals, as there has been an increased 3,666,378 Patented May 30, 1972 tendency for the units to elongate and shorten during SUMMARY OF THE INVENTION In its broadest concept, the present invention provides a friction anchor for a fluid operated downwell pump which utilizes an expandable sleeve which mates with a mating seal secured on the inside of the well casing or housing during operation of the pump so as to preclude gross movement of the pump and prevent chafing of the seals which maintain hydraulic circuitry on the outside diameter of the pump.

More particularly, the friction anchor of the present invention includes a seal secured to the inside of the well casing or housing in juxtaposition with at least a portion of the pump within the casing or housing to provide a gripping surface, a long, thin-walled expandable sleeve secured to the exterior surface of the pump and fitting closely with the mating gripping surface of the casing or housing seal, and a mandrel positioned inside of the expandable sleeve. The area between the mating surface of the casing or housing seal and the expandable sleeve defines a first chamber communicating with the low pressure pump discharge. A second chamber between the mandrel and the expandable sleeve communicates with the high pressure operating fluid. In practice, the expandable sleeve is free to move with little resistance so long as substantially no pressure differential exists between the first and second chambers.

When the pump is operational, high pressure is applied in the second chamber against the expandable sleeve and an actual interface fit between the expandable sleeve and the gripping surface of the casing or housing seal is simulated. Accordingly, during operation the pump is stabilized and immobilized and precluded from gross movement resulting from the tendancy of the pump to elongate and to shorten.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagramatic, partial vertical elevational view of a typical downwell pump in a bottom hole cavity with parts broken away.

FIG. 2 is an enlarged upper vertical sectional view, with parts broken away, taken on the line 22 of FIG. 1, having a friction anchor constructed in accordance with the present invention.

FIG. 3 is an enlarged perspective view showing the expandable sleeve and mandrel of the friction anchor of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning first to FIG. 1, a typical downwell pump 10 which will utilize the friction anchor of the present invention will be explained. However, while the friction anchor of the present invention will be described in connection with a particular downwell pump, it will, of course, be understood by one skilled in the art that the particular downwell pump does not constitute a limitation on the present invention.

As can be seen from FIG. 1, the typical downwell pump unit 10 is disposed within the bottom hole cavity of a Well casing or housing 12. The downwell pump unit 10 includes an outer casing 14 which has been divided by a packer 16 into an upper engine section 18 and a lower pump section 20. A source of operating fluid under pressure, which may be oil or water, from the surface is introduced into the engine section 18 from a fitting 22 having a central passage.

As is well known in the art, an engine cylinder 24 is carried within the engine section 18. Engine pistons of the differential type, whereby equal operating pressures on the two faces of each piston cause movement in one direction, are carried for reciprocation within the engine cylinder 24 and are connected to one or more pump pistons or plungers in the pump section 20 in the usual manner. A chamber within the engine cylinder 24 above the upper engine piston communicates with the various cylinders in which thhe engine pistons reciprocate, and as it is alternately pressurized and exhausted, the engine is caused to reciprocate. This in turn reciprocates the pump plungers in the lower pump section 20, causing oil to be pumped from the well.

As is well known in the art, the hydraulic circuitry of downwell pumps is established and maintained by seals 26 provided on the outside diameter of the unit which contact smooth sleeves within the bottom hole cavity well casing or housing. However, during the operation of a downwell pump, the seals 26 require constant maintenance because of the chafing which results from the tendency of the unit to elongate and shorten. The degree of this problem has been substantially increased because of the high performance units.

Turning now to FIG. 2, of the present invention, which is an enlarged upper vertical sectional view, with parts broken away, taken on the line 22 of FIG. 1, typical hydraulic circuitry seals 26 are shown on the outside diameter of the pump. The seals 26 contact smooth sleeves 28 and 30 within the bottom hole cavity well casing or housing 12. As can be seen, the seals 26 are provided with any desired back-up rings 32.

According to the present invention, the friction anchor includes the casing sleeve seal 30 having a gripping surface 31 secured to the inside of a sleeve of the casing or housing 12 in juxtaposition with at least a portion of the downwell pump 10. A long, thin-walled, expendable sleeve 34 is secured to the exterior surface of the pump and fits closely with the mating gripping surface 31 of the casing sleeve seal 30. The area between the mating surface 31 of the casing sleeve seal 30 and the expandable sleeve 34 defines a first chamber 36 which communicates with the low pump pressure discharge 38. A mandrel 40 is positioned inside of the expandable sleeve 34 and defines a second chamber 42 therebetween. The second chamber 42 communicates with the high pressure operating fluid 44 from the surface, which is introduced into the engine section 18 from the fitting 22.

The expandable sleeve 34, as best seen in FIG. 3, is preferably provided with a patterned surface 34a to let wiped-on low pressure oil escape and to provide a more satisfactory contact with the mating gripping surface 31 of the casing sleeve seal 30. In practice, it has been found that the patterned surface 34a preferably comprises a twodirectional, course, shallow helical spiral groove. Additionally, best results have been obtained when the casing sleeve seal 30 and the expandable sleeve 34 are made of hardened steel. This increases the coefiicient of the friction and the resulting anchoring force.

In practice, the expandable sleeve 34 is free to move with little resistance so long as substantially no pressure differential exists between the first and second chambers 36 and 42, which communicate with the low pressure pump discharge and with the high pressure operating fluid, respectively. However, when the pump is operational, the differential in pressure between the first and second chambers 36 and 42 causes the expandable sleeve 34 to expand against the gripping surface 31 of the casing sleeve seal 30, simulating an actual interface fit between the expandable sleeve 34 and the gripping surface 31 of the casing sleeve seal 30. The resultant anchoring force stabilizes and immobilizes the pump 10 during operation and precludes it from gross movement. Accordingly, the chafing of the hydraulic circuitry seals 26 is precluded,

which extends the life thereof and eliminates costly maintenance and well shut-down.

It will, of course, be understood that the resultant anchoring force of the friction anchor of the present invention is directly related to the area of surface in contact, i.e. the gripping surface 31 and the surface of the expandable sleeve 34, the pressure differential between the first and second chambers 36 and 42, which communicate with the low pressure pump discharge 38 and with the high pressure operating fluid 44, respectively, and the coefiicient of friction of the mating surfaces. Additionally, it will be uderstood that the expandable sleeve 34 at no time reaches its yield stress and that it returns to its original size upon the reduction of energizing pressure.

While a preferred application of the friction anchor of the present invention has been shown at the upper end of the typical downwell pump 10, it will, of course, also be understood that the friction anchor may be incorporated at any point along the pump 10 where a differential pressure is available.

While certain preferred embodiments of the invention have been specifically illustrated and described, it is understood that the invention is not limited thereto, as many variations will be apparent to those skilled in the art, and the invention is to be given its broadest interpretation within the terms of the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a free-type hydraulic pumping system of the type having a casing sleeve, a fluid operated downwell pump within said casing sleeve, said downwell pump having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, a discharge passage for carrying low pressure pump discharge, a source of operating fluid under high pressure, and a plurality of seals provided on the outside diameter of said pump to establish and maintain hydraulic circuitry, the improvement, in combination therewith, comprising a friction anchor, said friction anchor including a casing sleeve seal secured to the inside of said casing sleeve in juxtaposition with at least a portion of said pump to provide a gripping surface, a long, thin-walled, expandable sleeve secured to the exterior surface of said pump and fitting closely with the mating gripping surface of said casing sleeve seal, the area between said mating surface of said casing sleeve seal and said expandable sleeve defining a first chamber communicating with said low pressure pump discharge, and a mandrel positioned inside of said expandable sleeve and defining a second chamber therebetween, said second chamber communicating with said high pressure operating fluid, said expandable sleeve being free to move with little resistance so long as substantially no pressure differential exists between said first and second chambers, whereby when said pump is operational, the pressure differential between said first and second chambers results in the expansion of said expandable sleeve and the simulation of an actual interface fit between said expandable sleeve and the gripping surface of said casing sleeve seal, and said pump is stabilized and immobilized during operation and precluded from gross movement so as to prevent the chafing of said seals which maintain hydraulic circuitry.

2. The hydraulic pumping system according to claim 1, wherein the outer surface of said expandable sleeve is patterned to let wiped on low pressure oil escape so as to provide satisfactory contact.

3. The hydraulic pumping system according to claim 2, wherein the patterned surface of said expandable sleeve comprises a two-directional, coarse, shallow helical spiral groove.

4. The hydraulic pumping system according to claim 3, wherein said casing sleeve seal and said expandable sleeve are made of hardened steel so as to increase the coefii cient of friction and the resultant anchoring force.

5. The hydraulic pumping system according to claim 4, wherein said friction anchor is positioned at the upper end of said pump.

6. In combination, a casing sleeve, a hydraulic engine within said casing sleeve having a cylinder, a source of high pressure power fluid, a low pressure discharge, at least one piston slidable in said cylinder, a plurality of seals provided on the outside diameter of said hydraulic engine to establish and maintain hydraulic circuitry, and a friction anchor including a casing sleeve seal secured to the inside of said casing sleeve in juxtaposition with at least a portion of said hydraulic engine to provide a gripping surface, a long, thin-walled, expandable sleeve secured to the exterior surface of said hydraulic engine and fitting closely with the mating gripping surface of said casing sleeve seal, the area between said mating surface of said casing sleeve seal and said expandable sleeve defining a first chamber communicating with said low pressure dis charge, and a mandrel positioned inside of said expandable sleeve and defining a second chamber therebetween, said second chamber communicating with said high pressure power fluid, said expandable sleeve being free to move with little resistance so long as substantially no pressure differential exists between said first and second chambers, whereby when said engine is operational, the pressure differential between said first and second chambers results in the expansion of said expandable sleeve and the simulation of an actual interface fit between said expandable sleeve and the gripping surface of said casing sleeve seal and said engine is stabilized and immobilized during operation and precluded from gross movement so as to prevent the chafing of said seals which maintain hydraulic circuitry.

7. The structure according to claim 6, wherein the outer surface of said expandable sleeve is patterned to let wiped on low pressure oil escape so as to provide satisfactory contact.

8. The structure according to claim 7, wherein the patterned surface of said expandable sleeve comprises a twodirectional, coarse, helical spiral groove.

9. The structure according to claim 8, wherein said casing sleeve seal and said expandable sleeve are made of hardened steel so as to increase the coefficient of friction and the resultant anchoring force.

10. The structure according to claim 9, wherein said friction anchor is positioned at the upper end of said pump.

11. A friction anchor for a fluid operated downwell pump positioned within a casing sleeve, said downwell pump having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, a discharge passage for carrying low pressure pump discharge, a source of operating fluid under high pressure, and a plurality of seals provided on the outside diameter of said pump to establish and maintain hydraulic circuitry, which comprises a casing sleeve sealed secured to the inside of said casing sleeve in juxtaposition with at least a portion of said pump to provide a gripping surface, a long, thin-walled, expandable sleeve secured to the exterior surface of said pump and fitting closely with the mating gripping surface of said casing sleeve seal, the area between said mating surface of said casing sleeve seal and said expandable sleeve defining a first chamber communicating with said low pressure pump discharge, and a mandrel positioned inside of said expandable sleeve and defining a second chamber therebetween, said second chamber communicating with said high pressure operating fluid, said expandable sleeve being free to move with little resistance so long as substantially no pressure differential exists between said first and second chambers, whereby when said pump is operational, the pressure differential between said first and second chambers results in the expansion of said expandable sleeve and the simulation of an actual interface fit between said expandable sleeve and the gripping surface of said casing sleeve seal, and said pump is stabilized and immobilized during operation and precluded from gross movement so as to prevent the chafing of said seals which maintain hydraulic circuitry.

12. The friction anchor according to claim 11, wherein the outer surface of said expandable sleeve is patterned to let wiped on low presusre oil escape so as to provide satisfactory contact.

13. The friction anchor according to claim 12, wherein the patterned surface of said expandable sleeve comprises a two-directional, coarse, helical spiral groove.

14. The friction anchor according to claim 13, wherein said casing sleeve seal and said expandable sleeve are made of hardened steel so as to increase the coefficient of friction and the resultant anchoring force.

15. The friction anchor according to claim 14, wherein said friction anchor is positioned at the upper end of said pump.

References Cited UNITED STATES PATENTS 3,037,456 6/1962 Neilon 4l7358 3,299,956 l/l967 Howe 417-448 X ROBERT M. WALKER, Primary Examiner 

